1. Field of the Invention
This invention relates to a magnetic recording disk cartridge, and more particularly to a magnetic recording disk cartridge for a magnetic recording disk which is small in diameter and extremely thin in thickness and which is rotated at a high speed when recording and reproducing signals.
2. Description of the Prior Art
There has come into wide use, as a recording medium for computers, a flexible disk of polyester resin coated with magnetic material on both sides thereof, on which digital information is recorded by a magnetic head. This flexible disk, popularly referred to as a "floppy disk", is easy to handle and inexpensive.
Recently, there has been proposed a photographic still camera in which, instead of a conventional silver salt photographic film which cannot be reused, a magnetic recording disk smaller than the floppy disk both in thickness and diameter is used as a recording medium. This still camera is generally referred to as "an electronic camera" and is generally about as large as a typical 35 mm photographic camera. In the electronic camera the image of an object is magnetically recorded on the magnetic recording disk while the disk is rotated at a high speed. Generally the magnetic recording disk for the electronic camera is accommodated in a hard casing to form a cartridge and is loaded in the camera body together with the casing.
Though in the conventional floppy disk, the disk is provided with an engaging hole at its center to be supported on its both sides, the recording disk for the electronic camera is provided with a hub at its center, the hub being adapted to be engaged with a rotational shaft inserted into the cartridge from one side thereof.
In recording images using a magnetic recording medium, since video signals have a wider frequency band than digital signals or audio signals, the signals are densely recorded on the magnetic recording medium. Accordingly, when fine unevenness scratches or flaking exists in the magnetic coating on the magnetic recording medium or fine dust adheres thereto, so-called drop-out occurs during reproduction and the recorded signals cannot be faithfully reproduced. Since the magnetic recording disk cartridge for the electronic camera is frequently used outside, it is normally subjected to vibrations while being carried and the surface of the magnetic coating on the recording disk is apt to come into contact with the inner surface of the hard casing to be scratched thereby. Also, in an outdoor environment fine dust is apt to enter the casing through the magnetic head receiving opening or the hub hole exposing the hub.
There has been proposed in Japanese Utility Model Publication No. 57(1982)-102081 a magnetic recording disk cartridge in which a pad is attached to one of the opposed inner surfaces of the casing. However, this cartridge is mainly directed to preventing the recording medium from being scratched while being carried, and cannot prevent drop-out due to dust.